antioxidant properties of tropical and temperate herbal teas.pdf

8/11/2019 Antioxidant properties of tropical and temperate herbal teas.pdf

1/5

Short communication

Antioxidant properties of tropical and temperate herbal teas

E.W.C. Chan, Y.Y. Lim *, K.L. Chong, J.B.L. Tan, S.K. Wong

School of Science, Monash University Sunway Campus, Bandar Sunway, 46150 Petaling Jaya, Selangor, Malaysia

1. Introduction

For centuries, eastern countries have been using herbal

remedies to treat infections, ailments and diseases. Herbalremedies are often consumed in the form of tea, i.e. an infusion

of dried plant parts steeped in boiling water. Herbal teas have been

gaining popularity in western countries in recent years (Manteiga

et al., 1997). Hundreds of different herbal teas are sold in health

food stores. Available as pure or blended samples, herbal teas are

popular because of their fragrance, antioxidant properties and

therapeutic applications (Naithani et al., 2006; Aoshima et al.,

2007). Tea from Camellia sinensis is the most widely consumed

beverage in the world, second only to water (Muktar and Ahmad,

2000). It is an important dietary source of natural phenolic

antioxidants (Lachman et al., 2003; Dimitrios, 2006).

Extensive research has been carried out on the antioxidant

properties (AOP) of green and black C. sinensisteas (Manzocco et

al., 1998; Dufresne and Farnworth, 2001). AOP of herbal teas of

temperate plants, mainly of Lamiaceae, have been well studied

(Triantaphyllou et al., 2001; Atoui et al., 2005; Capecka et al.,

2005). AOP of tropical herbal teas have been studied less, with

some analyses carried out onAspalathus linearis(von Gadow et al.,

1997; Erickson, 2003); Cymbopogon citratus (Tsai et al., 2007;

Aoshima et al., 2007);Hibiscus sabdariffa (Aoshima et al., 2007);

Phyllanthus amarus (Lim and Murtijaya, 2007); Psidium guajava and

Toona sinensis (Chen et al., 2007); and Thunbergia laurifolia and

Orthosiphon aristatus (Chan and Lim, 2006).

In this study, AOP of thirteen tropical and five temperate herbal

teas were screened, with comparisons with green, oolong andblack teas of C. sinensis carried out as positive controls. The AOP

studied were total phenolic content, ascorbic acid equivalent

antioxidant capacity (AEAC), ferric-reducing power (FRP) and

ferrous ion-chelating (FIC) ability. This study, to the best of our

knowledge, represents the most comprehensive comparison

between AOP of tropical and temperate herbal teas in the

literature.

2. Materials and methods

2.1. Herbal and Camellia teas

Herbal teas, together with green, oolong and black teas ofC.

sinensisscreened for AOP are listed inTable 1. Tropical herbal teas

of misai kucing (O. aristatus), lemon grass (C. citratus), guava (P.

guajava), bitter gourd (Momordica charantia), lemon myrtle

(Backhousia citriodora),mas cotek (Ficus deltoidea),pegaga (Centella

asiatica) and rooibos (A. linearis); temperate herbal teas of

rosemary (Rosmarinus officinalis), peppermint (Mentha piperita),

mint (Mentha spicata), chamomile (Matricaria recutita) andoregano

(Origanum vulgare); and green, oolong and black teas ofC. sinensis

were purchased from the supermarket. Teas of getto (Alpinia

zerumbet) and rangjeud (T. laurifolia) were obtained from Okinawa

(Japan) and Bangkok (Thailand), respectively. Teas of legundi (Vitex

negundo) and asam gelugor (Garcinia atroviridis) were obtained

fromForest Research Institute Malaysia (FRIM). Driedflowers of jin

Journal o f Food Composition and Analysis 23 (2010) 185189

A R T I C L E I N F O

Article history:

Received 23 October 2008

Received in revised form 11 September 2009

Accepted 20 October 2009

Keywords:

Tropical teas

Temperate teas

Herbal teas

Camellia sinensis

Antioxidant activity

Food analysis

Food composition

A B S T R A C T

Antioxidant properties (AOP) of thirteen tropical and five temperate herbal teas were screened.

Comparisons were made with green, oolong and black teas ofCamellia sinensis. The AOP studied were

total phenolic content, radical-scavenging activity, ferric-reducing power and ferrous ion-chelating (FIC)

ability. Tropical herbal teas were more diverse in types and more variable in AOP values than temperateherbal teas. Herbal teas generally had lower antioxidant values than teas ofC. sinensis. Exceptions were

lemon myrtle, guava and oregano teas with AOP comparable to black teas. FIC ability of mint and

peppermint teas was significantly stronger than all C. sinensis teas.

2010 Elsevier Inc. All rights reserved.

* Corresponding author. Tel.: +60 3 55146103; fax: +60 3 55146364.

E-mail address: L [email protected] (Y.Y. Lim).

Contents lists available atScienceDirect

Journal of Food Composition and Analysis

j o u r n a l h o m e p a g e : w w w . e l s e v i e r . c o m / l o c a t e / j f c a

0889-1575/$ see front matter 2010 Elsevier Inc. All rights reserved.

doi:10.1016/j.jfca.2009.10.002
mailto:[email protected]://www.sciencedirect.com/science/journal/08891575http://dx.doi.org/10.1016/j.jfca.2009.10.002http://dx.doi.org/10.1016/j.jfca.2009.10.002http://www.sciencedirect.com/science/journal/08891575mailto:[email protected]


2/5

yin hua (Lonicera japonica) were purchased from the Chinese

medicine shop. In this study, tropical herbal teas included several

plant species from the subtropics such asB. citriodora,A. linearis,A.

zerumbet and L. japonica. Teas ofC. sinensis, a tropical and sub-

tropical species, are not considered as herbal teas.

2.2. Extraction of teas

In tea extraction, 1 g of tea in powder form was extracted with50 mL boiling water. Infusions were allowed to steep for 1 h with

continuous swirling. Extracts were filtered and stored at 4 8C for

further analysis. Analyses of aqueous tea extracts were done in

triplicate.

2.3. Extraction efficiency

Extraction efficiency of boiling water was testedwith Bohgreen

tea. After the first extraction, the residues were filtered and

extracted successively for the second and third time. Extraction

efficiency in percent was based on total phenolic content of first,

second and third extractions.

2.4. Antioxidant properties of teas

Total phenolic content (TPC) was determined using the Folin-

Ciocalteu assay (Kahkonen et al., 1999). Samples (300mL, in

triplicate) were introduced into test tubes followed by 1.5 mL of

Folin-Ciocalteus reagent (10 times dilution) and 1.2 mL of sodium

carbonate (7.5%, w/v). The tubes were allowed to stand for 30 min

before absorbance at 765 nm was measured. TPC was expressed as

gallic acid equivalent (GAE) in mg per 100 g material. The

calibration equation for gallic acid was y= 0.0111x 0.0148

(R2 = 0.9998), where y is the absorbance and x is the gallic acid

concentration in mg/L.

Radical-scavenging activity (RSA) was assessed using the 2,2-

diphenyl-1-picrylhydrazyl (DPPH) assay (Miliauskas et al., 2004).

Different dilutions of extracts (1 mL) were added to 2 mL of DPPH

(5.9 mg per 100 mL methanol). After 30 min, absorbance was

measured at 517 nm. RSA, expressed as ascorbic acid equivalent

antioxidant capacity (AEAC) in mg ascorbic acid/100 g, was

calculated as IC50(ascorbate)/IC50(sample) 105. IC50 of ascorbic acid

was 0.00387 mg/mL.

For assessing ferric-reducing power (FRP), the assay described

by Chu et al. (2000)was adapted. Different dilutions of extracts

(1 mL) were added to 2.5 mL phosphate buffer (0.2 M, pH 6.6) and

2.5 mL of potassium ferricyanide (1%, w/v). The mixture wasincubated at 50 8C for 20 min. After trichloroacetic acid solution

(2.5 mL, 10%, w/v) was added, the mixture was separated into

aliquots of 2.5 mL anddilutedwith 2.5 mL of water.To each diluted

aliquot, 500mL of ferric chloride solution (0.1%, w/v) was added.

After 30 min, absorbance was measured at 700 nm. FRP of extracts

was expressedas mg GAE/g. The calibration equation for gallic acid

wasy = 16.767x (R2 = 0.9974), where y is the absorbance and x is

the gallic acid concentration in mg/mL.

The ferrous-ion-chelating (FIC) assay was adapted from Singh

and Rajini (2004). FIC ability was determined by mixing FeSO4(0.1 mM, 1 mL) with different dilutions of extracts (1 mL), followed

by ferrozine (0.25 mM, 1 mL). Absorbance was measured at 562 nm

after 10 min. The ability of extracts to chelate ferrous ions was

calculated as chelating effect % = (1Asample/Acontrol) 100. FICability was expressed as chelating EC50 (CEC50) in mg/mL, or the

effective concentration of extract to chelate ferrous ions by 50%.

3. Results and discussion

Based on three successive extractions of Boh green tea (1 g)

with boiling water (50 mL) for 1 h, TPC of first, second and third

extractions was found to be 75 1.3, 17 0.5 and 8 0.7%,

respectively. As the yield of first extraction was high, all analyses

of teas were extracted with boiling water. Significantly higher yields

of hot water than cold water extraction of green tea (Lin et al., 2008)

and stronger RSA of oolong teaextracted with hot water of increasing

temperature (Su et al., 2006) have been reported. For green, oolong

and black teas, extraction with water at 100 8

C for 3 min yielded

Table 1

Types of tropical and temperate herbal teas, and green, oolong, and black teas ofCamellia sinensis screened for antioxidant properties.

Type of tea Species (family) Part used and life-form Company, country

Tropical herbal tea

Lemon myrtle Backhousia citriodora(Myrtaceae) Leaf, shrub Boh, Malaysia

Guava Psidium guajava(Myrtaceae) Leaf, tree Organic Herb, Malaysia

Legundi Vitex negundo (Lamiaceae) Leaf, tree FRIM, Malaysia

Rooibos Aspalathus linearis (Leguminosae) Leaf, shrub Dr Nortier, S. Africa

Jin yin hua Lonicera japonica(Caprifoliaceae) Flower, vine Ren ZK, Malaysia

Misai kucing Orthosiphon aristatus(Lamiaceae) Leaf, herb Pure Herb, MalaysiaPegaga Centella asiatica(Apiaceae) Leaf, herb BZest, Malaysia

Mas cotek Ficus deltoidea (Moraceae) Leaf, shrub CBintik, Malaysia

Bitter gourd Momordica charantia(Cucurbitaceae) Fruit, vine Everjoy, Vietnam

Getto Alpinia zerumbet(Zingiberaceae) Leaf, herb Nakazen, Japan

Asam gelugor Garcinia atroviridis (Guttiferae) Leaf, tree FRIM, Malaysia

Rang jeud Thunbergia laurifolia(Thunbergiaceae) Leaf, vine TriSiam, Thailand

Lemon grass Cymbopogon citratus(Graminae) Stem, herb Organic Herb, Malaysia

Temperate herbal tea

Oregano Origanum vulgare(Lamiaceae) Leaf, herb McCormack, US

Mint Mentha spicata(Lamiaceae) Leaf, herb McCormack, US

Peppermint Mentha piperita(Lamiaceae) Leaf, herb Twinings, UK

Rosemary Rosmarinus officinalis(Lamiaceae) Leaf, herb McCormack, US

Chamomile Matricaria recutita(Asteraceae) Flower, herb Dilmah, S. Lanka

Camellia tea

Green Tea (g) Camellia sinensis(Theaceae) Leaf, shrub Boh, Malaysia

Green Tea (g) Sea Dyke, China

Ti Kuan Yin (o) Sea Dyke, China

Yellow Label (b) Lipton, Thailand

Cha Wang (o) An Xi, China

Bukit Cheeding (b) Boh, Malaysia

Cameron Highlands (b) Boh, Malaysia

E.W.C. Chan et al./ Journal of Food Composition and Analysis 23 (2010) 185189186


3/5

higher total flavan-3-ol content than extraction with water at 60 and

80 8C(Horzicet al., 2009).

Tropical herbal teas screened were diverse in types, parts used

andmorphology. They comprised leaves, flowers, fruits andstems

of 13 species of trees, shrubs, vines and herbs belonging to 13

genera and 11 families (Table 1). AOP were variable with TPC,AEAC andFRP values rangingfrom 644to 7560 mg GAE/100 g, 354

to 13,600 mg AA/100 g and 3 to 61 mg GAE/g, respectively (Table

2). Teasof Myrtaceae (lemon myrtle andguava) displayed thebest

TPC,RSA and FRP, with valuesranging from 5930 to7560 mgGAE/

100 g, 7430 to 13,600 mg AA/100 g and 35 to 61 mg GAE/g,

respectively. Getto, mas cotek, misai kucing, lemon myrtle and

guava teas displayed strong FIC ability with CEC50values ranging

from 0.9 to 1.2 mg/mL. Their strong AOP could be due to the

contentand compositionof major phenolic compounds (Table 3).

Temperate herbalteas screened were less diverse in types,parts

used and morphology. They comprised leaves and flowers of fivespecies of herbs belonging to four genera and two families,

Lamiaceae being dominant (Table 1). AOP were less variable with

TPC, AEAC and FRP values ranging from 1370 to 5860 mg GAE/

100 g, 966to 7240 mgAA/100 g and8 to 49 mg GAE/g,respectively

(Table 2). Temperate herbal teas of oregano, mint and peppermint

Table 2

Total phenolic content (TPC), ascorbic acid equivalent antioxidant capacity (AEAC), ferric-reducing power (FRP), and chelating EC50(CEC50) of tropical and temperate herbal

teas.

Type of tea TPC (mg GAE/100 g) AEAC (mg AA/100 g) FRP (mg GAE/g) CEC50(mg/mL)

Tropical herbal tea

Lemon myrtle 7560126a 13 600792a 610.6a 1.20.2a

Guava 5930584b 7430752b 352.7b 1.20.2a

Legundi 5420404b 4900549c 302.0c 1.90.1b

Rooibos 3750235c 3020456e 200.4e 4.71.2d

Jin yin hua 3630

169c 3850

224d 21

0.5d 2.0

0.2bMisai kucing 278071d 4160362cd 220.9d 1.10.5a

Pegaga 2040214e 1340613f 121.2f 2.70.1c

Mas cotek 202087e 108066f 5.90.3h 1.00.0a

Bitter gourd 143030f 110063f 100.4g 2.00.1b

Getto 85421g 53656g 3.50.3i 0.90.1a

Asam gelugor 80694g 26215i 2.90.2j >7.0e

Rang jeud 80550g 59129g 4.30.5i 4.00.5d

Lemon grass 64420h 35431h 3.10.2j 4.70.3d

Temperate herbal tea

Oregano 5860379a 7240309a 491.6a 0.80.2b

Mint 435020b 4430310c 310.4c 0.30.0a

Peppermint 4210139b 6040311b 370.3b 0.40.1a

Rosemary 281089c 309097d 201.2d 2.10.5c

Chamomile 137037d 96652e 8.10.2e 3.30.1d

Camellia tea

Green Tea (g) 14,1201810a 25 0002780a 14311a 1.80.3c

Green Tea (g) 11,3701480b 18 4601740b 8411b 1.40.1b

Ti Kuan Yin (o) 9090457c 16 1702480b 694.2c 1.90.2c

Yellow Label (b) 8490803c 11 5501150cd 533.0e 1.70.1c

Cha Wang (o) 7500462d 14 4503046bc 592.3d 1.80.5c

Bukit Cheeding (b) 7410120d 10 300563d 533.0e 1.00.2a

Cameron Highlands (b) 6060543e 75101260e 362.4f 1.50.2bc

Teas are ranked based on TPC and values are means SD (n = 3). For each column, values followed by the same letter are not statistically different atP


4/5

displayed strong AOP with outstanding CEC50 values of 0.8, 0.3 and

0.4 mg/mL, respectively. With the exception of chamomile tea

(Asteraceae), rosmarinic acid is one of the major phenolic

compounds in all the other herbal teas (Lamiaceae) (Table 3).

The strong AOP of temperate herbal teas might be attributed to the

predominance of rosmarinic acid and other phenolic acids.

With higher percentage of teas having strong AOP, particularly

in FIC ability, temperate herbal teas investigated were superior to

tropical herbal teas. Temperate herbal teas with strong primary

AOP (RSA andFRP) also hadstrong secondaryAOP (FIC ability). This

was not evident in tropical herbal teas as some teas with strong

primary AOP displayed poor secondary AOP (e.g. rooibos tea) and

vice versa (e.g. getto tea). RSA and FRP are measures of the

hydrogen and electron-donating abilities of primary antioxidants,

respectively (Lim et al., 2007). FIC ability measures the ability of

secondary antioxidants to chelate metal ions. Primary antioxidants

prevent oxidative damage by directly scavenging free radicals,

while secondary antioxidants act indirectly by preventing the

formation of free radicals through Fentons reaction.

Teas ofC. sinensishad TPC, AEAC, FRP and CEC50values ranging

from 6060 to 14,120 mg GAE/100 g, 7510 to 25,000 mg AA/100 g,

36 to 143 mg GAE/g and 1.0 to 1.9 mg/mL, respectively (Table 2).

Ranking of TPC, RSA, FRP and FIC ability was green > oolong -

black; green oolong > black; green > oolong > black; andblack > green oolong, respectively. Findings from this study

deviated fromYen and Chen (1995)who reported that ranking of

RSA was green > oolong > black, and ranking of reducing power

was oolong > green > black; and fromvonGadow et al. (1997) and

Yokozawa et al. (1998), who reported that ranking of RSA was

green > black > oolong. Green teas have been reported to have

significantly higher TPC, RSA and FRP, but poorer FIC ability, than

black teas (Chan and Lim, 2006; Chan et al., 2007).

The outstanding AOP of green, oolong and black teas of C.

sinensis could be attributed to their high flavanol content of

epigallocatechin gallate (EGCG), epigallocatechin (EGC) and

gallocatechin (GC) (Table 3). Recently, Horzic et al. (2009)

reported that green, oolong and black teas, extracted with

deionised water heated to 100 8C for 3 min, had total identifiedflavan-3-ol contents of 999, 666 and 672 mg/L, respectively.

Temperate herbal teas of linden and chamomile yielded flavan-3-

ol contents of only 127 and 22 mg/L, respectively.

Compared to teas ofC. sinensis, tropical and temperate herbal

teas generally had lower antioxidant values. Exceptions were

lemon myrtle, guava and oregano teas with AOP comparable to

black teas. CEC50 values of mint and peppermint were significantly

larger than all C. sinensis teas. FIC ability of oregano, getto, mas

cotek, misai kucing, lemon myrtle and guava teas was comparable

to black teas. It can be seen that some tropical and temperate

herbal teas had AOP that are superior or comparable to green,

oolong and black teas.

In conclusion, tropical herbal teas were more diverse in types

and more variable in AOP than temperate herbal teas. Herbal teasgenerally had lower antioxidant values than teas ofC. sinensis.

Acknowledgements

The authors are thankful to Monash University Sunway Campus

(MUSC) Malaysia for financial support of this project, to Forest

Research Institute Malaysia (FRIM) for providing tea samples of

legundi and asam gelugor, and to Dr. Mami Kainuma for

purchasing the getto tea from Okinawa, Japan.

References

Akowuah, G.A., Ismail, Z., Norhayati, I., Sadikun, A., 2005. The effects of differentextraction solvents of varying polarities on polyphenols ofOrthosiphon stami-

neusand evaluation of the free radical-scavenging activity. Food Chemistry 93,311317.

Aoshima, H., Hirata, S., Ayabe, S., 2007. Antioxidative and anti-hydrogen peroxideactivities of various herbal teas. Food Chemistry 103, 617622.

Areias, F.M., Valentao, P., Andrade, P.B., Ferreres, F., Seabra, R.M., 2001. Phenolicfingerprint of peppermint leaves. Food Chemistry 73, 307311.

Atoui,A.K., Mansouri,A., Boskou, G.,Kefalas, P.,2005.Tea andherbal infusions: theirantioxidant activity and phenolic profile. Food Chemistry 89, 2736.

Bramati, L., Minoggio, M., Gardana, C., Simonetti, P., Mauri, P., Pietta, P., 2002.Quantitative characterization of flavonoid compounds in rooibos tea (Aspa-lathus linearis) by LC-UV/DAD. Journal of Agricultural and Food Chemistry 50,

55135519.Capecka,E., Mareczeek, A.,Leja,M., 2005. Antioxidant activity of freshand dryherbsof some Lamiaceae species. Food Chemistry 93, 223226.

Chan, E.W.C., Lim,Y.Y., 2006.Antioxidant activity ofThunbergia laurifolia tea.Journalof Tropical Forest Science 18, 130136.

Chan, E.W.C., Lim, Y.Y., Chew, Y.L., 2007. Antioxidant activity ofCamellia sinensisleaves and tea from a lowland plantation in Malaysia. Food Chemistry 102,12141222.

Chen, H.Y., Lin, Y.C., Hsieh, C.L., 2007. Evaluation of antioxidant activity of aqueousextract of some selected nutraceutical herbs. Food Chemistry 104, 14181424.

Chu, Y.H., Chang, C.L., Hsu, H.F., 2000. Flavonoid content of several vegetables andtheir antioxidant activity. Journal of the Science of Food and Agriculture 80,561566.

DamienDorman, H.J.,Kosar, M., Kahlos, K., Holm,Y., Hiltunen, R., 2003. Antioxidantproperties and composition of aqueous extracts from Menthaspecies, hybrids,varieties, and cultivars. Journal of Agricultural and Food Chemistry 51, 45634569.

Dimitrios, B., 2006.Sources of natural phenolic antioxidants. Trends in Food Scienceand Technology 17, 505512.

Dufresne, C.J., Farnworth, E.R., 2001. A review of latest research findings on thehealthpromotion propertiesof tea. Journal of NutritionalBiochemistry12, 404421.

Erickson, L., 2003. Rooibos tea: research into antioxidant and antimutagenicproperties. HerbalGram 59, 3445.

Horzic, D., Komes, D., Belscak, A., Ganic, K.K., Ivekovic, D., Karlovic, D., 2009. Thecomposition of polyphenols and methylxanthines in teas and herbal infusions.Food Chemistry 115, 441448.

Kahkonen, M.P., Hopia, A.I., Vuorela, H.J., Rauha, J.P., Pihlaja, K., Kujala, T.S.,Heinonen, M., 1999. Antioxidant activity of plant extracts containing pheno-lic compounds. Journal of Agricultural and Food Chemistry 47, 39543962.

Kim, W.J., Kim, J., Veriansyah, B., Kim, J.D., Lee, Y.W., Oh, S.G., Tjandrawinata, R.R.,2009. Extraction of bioactive components fromCentella asiaticausing subcriti-cal water. Journal of Supercritical Fluids 48, 211216.

Kubola, J., Siriamornpun, S., 2008. Phenolic contents and antioxidant activities ofbitter gourd (Momordica charantia L.) leaf, stem and fruit fraction extracts invitro. Food Chemistry 110, 881890.

Lachman, J., Orsak, M., Pivec, V., Dudjak, J., Krym, O., 2003. Polyphenol content ingreen, black and oolong tea (Camelia sinensis/L./Kuntze) infusions in different

times of tea maceration. Scientia Agriculturae Bohemica 34, 2228.Liang, Q., Quian, H., Yao, W., 2005. Identification of flavonoids and their glycosides

by high-performance liquidchromatographywith electrospray ionization massspectrometry and with diode array ultraviolet detection. European Journal ofMass Spectrometry 11, 93102.

Lim, Y.Y., Lim, T.T., Tee, J.J., 2007. Antioxidant properties of several tropical fruits: acomparative study. Food Chemistry 103, 10031008.

Lim, Y.Y., Murtijaya, J., 2007. Antioxidant properties ofPhyllanthus amarusextractsas affected by different drying methods. LWTFood Science and Technology 40,16641669.

Lin, S.D.,Liu, E.H.,Mau, J.L.,2008.Effectof differentbrewingmethodson antioxidantproperties of steaming greentea. LWTFood Science andTechnology 41,16161623.

Manteiga, R., Park, D.L., Ali, S.S., 1997. Risks associated with consumption of herbalteas. Reviews of Environmental Contamination and Toxicology 150, 130.

Manzocco, L., Anese, M., Nicoli, M.C., 1998. Antioxidant properties of tea extracts asaffected by processing. LWTFood Science and Technology 31, 694698.

Marques, V., Farah, A., 2009. Chlorogenicacids and related compounds in medicinal

plants and infusions. Food Chemistry 113, 13701376.McKay, D.L., Blumberg, J.B., 2006. A review of the bioactivity and potential healthbenefits of chamomile tea (Matricaria recutita L.). Phytotherapy Research 20,519530.

Miliauskas, G., Venskutonis, P.R., van Beek, T.A., 2004. Screening of radical scaveng-ing activity of some medicinal and aromatic plant extracts. Food Chemistry 85,231237.

Muktar, H., Ahmad,N., 2000. Tea polyphenols: prevention of cancer and optimizinghealth. American Journal of Clinical Nutrition 71, 1698S1702S.

Naithani, V., Nair, S., Kakkar, P., 2006. Decline in antioxidant capacity of Indianherbal teas during storage and its relation to phenolic content. Food ResearchInternational 39, 176181.

Singh, N., Rajini, P.S., 2004. Free radical scavenging activity of an aqueous extract ofpotato peel. Food Chemistry 85, 611616.

Su, X., Duan, J., Jiang, Y., Shi, J., Kakuda, Y., 2006. Effects of soaking conditions on theantioxidant potentials of oolong tea. Journal of Food Composition and Analysis19, 348353.

Tiwari, O.P.,Tripathi,Y.B., 2007.Antioxidant propertiesof different fractionsofVitexnegundo Linn. Food Chemistry 100, 11701176.

E.W.C. Chan et al./ Journal of Food Composition and Analysis 23 (2010) 185189188


5/5

Triantaphyllou, K., Blekas, G., Boskou, D., 2001. Antioxidative properties of waterextracts obtained from herbs of the species of Lamiaceae. International Journalof Food Science and Nutrition 52, 313317.

Tsai, P.J., Tsai, T.H., Yu, C.H., Ho, S.C., 2007. Comparison of NO-scavenging and NO-suppressing activities of different herbal teas with those of green tea. FoodChemistry 103, 181187.

von Gadow, A., Joubert, E., Hansmann, C.F., 1997. Comparison of the antioxidantactivity of rooibos tea (Aspalathus linearis) with green, oolong and black tea.Food Chemistry 60, 7377.

Yen, G.C., Chen, H.Y., 1995. Antioxidant activity of various tea extracts in relationto their antimutagenicity. Journal of Agricultural and Food Chemistry 43, 2732.

Yokozawa, T., Dong, E., Nakagawa, T., Kashiwagi, H., Nakagawa, H., Takeuchi, S.,Chung, H.Y., 1998. In vitro and in vivo studies on the radical scavengingactivity of tea. Journal of Agricultural and Food Chemistry 46, 21432150.

Zheng, W., Wang, S.Y., 2001. Antioxidant activity and phenolic compounds inselected herbs. Journal of Agricultural and Food Chemistry 49, 51655170.

E.W.C. Chan et al./ Journal of Food Composition and Analysis 23 (2010) 185189 189

antioxidant properties of tropical and temperate herbal teas.pdf

Documents